Corner beads used as trim strips in drywall construction are normally either a "nail-on" type or a "tape-on" type. Nail-on beads commonly take the form of an angle strip of metal with side flanges meeting at a center corner rib providing shoulders against which spackle or joint cement can be dressed when feathered from the adjoining wall surfaces to cover the edges and outer faces of the side flanges and the heads of the nails securing these flanges to the wall structure. These nails are usually driven through the bead flanges at intervals of no more than eight inches.
Tape-on corner beads utilize paper wings to secure a metal corner angle in position rather than using nails. These wings are lateral extensions of a paper cover strip which is bonded by a hot melt glue or other suitable adhesive to the metal corner angle, usually on the outer faces of the side flanges. Spackle or joint cement and wall paint for dressing and finishing the corner, normally adhere significantly better to the paper cover strip of tape-on beads than to the exposed metal of nail-on beads. Also, normally drywall corners covered with nail-on beads are more susceptible to developing crack lines along the outer edges of the side flanges than when tape-on beads are used. On the other hand, nail-on beads have the advantage of requiring less skill to apply.
Corner beads are used not only to cover outside and inside corners at the intersections of wallboard panels, but also, to cover the raw edge of a vertical wallboard panel which is spaced by a narrow gap from a ceiling or other building part. In such an instance normally one of the bead flanges overlies the panel edge and the other flange overlaps the adjoining panel face. The latter flange is normally dressed over by spackle or joint, cement, and paint during a finishing operation. There is a need during this finishing operation to cover the ceiling or other related building part so as to protect it from being spattered by the finishing materials. This has been done in the past by applying masking tape independently of the corner bead or by providing the bead with a removable masking element projecting oppositely from the bead flange which covers the panel edge.
For example, in U.S. Pat. No. 4,074,478 a nail-on type of angle trim made of vinyl has a tearaway strip extending integrally from the elbow of the trim, thereby forming a generally T-shaped product. The tearaway strip is severed after installation of the trim by tearing it away at a score line formed at the trim elbow.
U.S. Pat. No. 5,243,797 discloses a nail-on type of metal corner bead having two metal flanges meeting at an elbow and having one of these flanges wider than the other one and doubled back over itself to provide a slot at the overlap for holding a masking strip of paper or thin metal which projects beyond the elbow to provide a masking portion. After the finishing operation the masking strip is pulled free of the slot.
The Beadex Manufacturing Company, Renton, Wash., has manufactured and sold a tape-on strip known as the "Jambex Pre-Mask" in which one of the paper wings of a tape-on corner bead has been widened so that it could be doubled back over itself to provide a masking portion extending oppositely from the elbow of the bead relative to the metal flange to which the wing is attached. After the finishing operation the masking portion is removed by cutting it along the elbow of the trip strip with a razor blade knife. The principal object of the present invention is to provide an improved tape-on angle trim having an integral tearaway masking element that can easily be removed without using a cutting tool and leaves a finished appearance at the elbow of the strip.